https://www.um.edu.mt/library/oar/handle/123456789/49432 2026-06-04T10:19:10Z 2026-06-04T10:19:10Z https://www.um.edu.mt/library/oar/handle/123456789/120258 2024-04-03T06:19:53Z 2019-01-01T00:00:00Z

Title: Optimization of a three-axes teslameter for the calibration of the next generation undulators Abstract: The measurement of a magnetic field in three-axes and with high spatial resolution has several industrial and experimental applications. One specific experimental application involves characterizing the field map of insertion devices in free electron lasers. This work presents the development of a new, reduced form-factor, three-axes digital teslameter. This instrument will be used to characterize the SwissFEL insertion devices at the Paul Scherrer Institute (PSI) for the Athos soft X-ray beamline. Together with a Hall probe at the centre of the cross-sectional area of the undulator, the setup will traverse along the full undulator length on a specifically designed rig with minimal vibrations, thus acquiring a full magnetic field map in the three-axes. The teslameter incorporates analogue signal conditioning for the three-axes interface to a Hall probe, a linear absolute encoder interface and a high resolution 24-bit analogue-to-digital converter. This contrasts to the old instrumentation setup used which only consists of the analogue circuitry with digitization being done externally to the instrument by proprietary hardware. The new instrument also provides a very accurate magnetic field map in the µT range with simultaneous readings from the position encoder at an accuracy of ±3 µm. The novelty of the instrument is the provision of an integrated tailored solution which is very compact in size and with comparable performance to the best state-of-the-art teslameters that are currently available on the market. This dissertation presents the development of a novel teslameter followed by a detailed and standardized calibration procedure that is critical in optimizing the performance of this precision instrument. The performance results obtained outline the noise, measuring precision, repeatability and frequency response of the instrument among other parameters. These are analysed to finally devise the insightful knowledge on the magnetic properties of insertion devices that need to be modelled and characterised. Description: M.Sc.(Melit.)

2019-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/98672 2022-07-04T06:10:14Z 2019-01-01T00:00:00Z

Title: Towards robot-assisted living through universal design of the environment Abstract: More seniors citizens are living alone in their own house, compared to any other population group. Depending on the severity of their health condition, these people may be able to perform the physical self-maintenance activities of daily living, such as bathing, dressing and feeding, but may encounter difficulties in performing the more challenging Instrumental Activities of Daily Living, IADLs , which include telephone use, food preparation, housekeeping, laundry and responsibility for own medication. The ability to perform the IADLs is very important for individuals who wish to live independently and to form part of their community. Hence, they might need to rely on outside assistance (e.g. family, friends, and/or social services) if they are to continue living independently in their own residence. As a result, researchers are looking into assistive technology that can help older adults (OAs) in day-to-day tasks. Significant research has been done on assistive technology. However, only a few robots are in actual use. This is because the robot must operate in an environment that was not intended for it. This presents a number of challenges with regard to observability, manipulability, accessibility, activity and safety, which the robot must be equipped to handle in order to be successfully deployed in the home environment. Hence, researchers are looking into the concept of universal design, where an environment is designed to satisfy the needs of all its users, including the robot. Still, the environment must still be usable by humans, safe, aesthetically pleasing, functional and offered at a reasonable price. The objective of this research was to develop a framework for the introduction of robots into the home to provide assistance in performing IADLs. The framework was evaluated through a partial prototype system, encompassing a prototype tele-operated mobile assistive robot designed to provide physical support to the older people living at home, and a partial prototype of the optimised environment. A survey was first carried out with a sample of older people who would benefit from this assistive robot and of allied healthcare professionals, so as to determine the appearance of the robot and to identify the minimum subset of movements that the robot must be able to perform. This is because both the appearance and the usefulness of the robot play a crucial role in the OA’s acceptance of robot-assisted living. The designed assistive robot, named MARIS, for Mobile Assistive Robot in an Inclusive Space was able to perform a number of different activities facilitated by the designed environment. Description: M.SC.ENG.

2019-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/98670 2022-07-04T06:09:48Z 2019-01-01T00:00:00Z

Title: Investigating the influence of mooring design on floating wind turbine aerodynamics Abstract: Mooring lines are essential in the design of Offshore Floating Wind Turbines (OFWT). These provide both the necessary station-keeping and stability to the structure. Hence, understanding the influence of the mooring configuration on the whole OFWT is crucial to balance energy generation and costs. In this dissertation, a simulation analysis was done to analyse the effects incurred on the aerodynamic performance of a semi-submersible platform with regards to the mooring design. An OFWT was modelled using ANSYS Aqwa which uses hydrodynamic diffraction and radiation principles to compute the hydrodynamic loading on the structure. The aerodynamic loads were computed using an open source free-wake vortex code, Wake Induced Dynamic Simulation (WInDS) in which the unsteady aerodynamic wake was modelled using free wake vortex methods with which the aerodynamic loads on the rotor were computed. A manually coupled model was developed which combined the hydrodynamic loading and the aerodynamic performance of the OFWT. The model was validated with literature to ensure that the results were as close as possible to those observed in reality. Tests were compiled for different mooring conditions in different wind and wave environments. Using the results obtained for the thrust and power generated by the OFWT together with the displacements of the OFWT in the surge, heave and pitch degrees of freedom, the influence of the mooring design was analysed. Description: M.SC.ENG.

2019-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/98654 2022-07-04T06:09:14Z 2019-01-01T00:00:00Z

Title: Study of shot-peened and PVD coated aerospace-grade titanium alloy Abstract: Titanium alloys are extensively used in the aerospace industry due to their unique combination of physical and metallurgical properties that enables weight saving in various highly stressed aircraft components. However, the metal is characterised by poor tribological properties that limit its application in sliding components. To solve this problem, engineers resort to surface engineering techniques such as nitriding and physical vapour deposition (PVD) of hard, wear resistant coatings. Nonetheless, improvement in the wear resistance is usually seconded by a drop in the fatigue properties. On the contrary, surface engineering techniques such as shot-peening are designed to induce compressive residual stresses at the surface of the material, which increase the material’s resistance against fatigue. Consequently, the aim of this research was to develop a hybrid treatment consisting of deposition of a tungsten-doped diamond like carbon coating (WC/C) by PVD on shot-peened Ti-6Al-4V surfaces and assess its impact on the fatigue strength. The main factors affecting the fatigue performance were highlighted and characterisation of shot-peened, WC/C coated and hybrid treated surfaces was carried out. Residual stresses, being one of the key properties that dictate the fatigue performance of a material were measured by X-ray diffraction (XRD). Rotating bending fatigue tests were carried out and the fatigue performance was analysed by combination of S-N diagrams and in-depth fractographic analysis. Results show that despite the pronounced surface roughness produced by the shot-peening treatment, the high residual compressive stresses, together with the refined and cold-worked microstructure confirmed by electron backscatter diffraction (EBSD), were capable of improving (3.8% improvement in the fatigue limit as compared to the untreated condition) the fatigue performance of the shot-peened Ti6Al-4V alloy. Conversely, the WC/C coating displayed extensive cracking which propagated prematurely into the substrate and yielded a 4% drop in the fatigue limit. On the other hand, despite the annealing of a fraction of the beneficial compressive residual stresses during the coating deposition treatment, the hybrid treatment yielded a 2.4% improvement in the fatigue limit over the untreated condition. This result coupled with the high coating hardness and adhesion confirm the capability of this hybrid treatment in improving both the tribological and fatigue performance of the Ti6Al-4V alloy. Description: M.SC.ENG.

2019-01-01T00:00:00Z